Double reentrant cone loud speaker



June 9, 1931. A. M L. NICOLSON DOUBLE REENTRANT CONE LOUD SPEAKER v Filed March 17, 1927 2 Sheets-Sheet 2 l Y mm R Er... VL T N .T IM 0A WYM - vice or a plurality of such Patented June 9, 1931 more sea,

ALEXANDER MCLEALT NICOLSON,

OF NEW YORK, N. Y., ASSIGNOB, BY. MESNE A STGN- DOUBLE BEENTBANT CONE LOUD SPEAKER Application filed March 17, 1927. Serial No. 175,989.

This invention relates to apparatus for reversibly producing sound from electrical oscillations corresponding thereto, and; more particularly to such apparatus usually designated as loud speakers, adapted to reproduce sound comparable in quality and intensity with the original sounds to be reproduced.

It is an object of this invention to provide a diaphragm having a plurality of parts or active sound radiating elements, front and rear, separated by a distance considerably greater than the thickness of the material constituting the diaphragm.

It is a further object of this invention to provide such apparatus in vwhich the driving mechanism is mounted and contained entirely in the space betweenthe front and rear surface of the diaphragm. It is still a further object of this invention to provide such apparatus inwhich a piezo-electric crystal dedevices are used in the diaphragm. v

The features of novelty which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. My invention itself, however, both as to its fundamental principles and as to its practical application will best be understood by reference to the specification and aoompanying drawings, in which: 1

Figures 1 and 2 are respectively frontand side elevations of one form of apparatusaccording to my invention, the latter 'figure being partly in section;

Fig. 3 is a top plan view of the same, partly in section;

Fig. i is a front elevation-of a modified form of apparatus according to my invention.

Fig. 5 is thereof. 1 v p I In acordance with my invention, I provide a plurality of conical diaphragms of suitable material, such as paper, cardboard, wood, composition, or metal if desired. The diaphragms are constructed so as to havethe same diameter at the periphery but different altitudes, and are mounted preferably with their peripheries cemented or otherwise sea pi p View partly in section cured together so to form a single unit. The difference in altitude is so chosen that a space is formed between theapexes, which are dis posed on the same side of the peripheral plane, and the driving means is mounted within this space.

In its simplest form, the driving means may comprise a piezo-electric crystal pro- -vided with a stress plate and driving rod connected to the apexes of the diaphragm, but it will be clear that other means may be used in place of the piezo-electric crystal, such for example, as a driving unit of the electro-magnetic type. lVhen electrical oscillations are supplied to the piezo-electric crystal device,

vibrations corresponding thereto are produced as is well known in the art.

These vibrations are apexes of the cones constituting the diaphragmand set up stress'waves in the material, which travel from the apex outwardly toward the peripheries. It will be noted that since the paths which must be traversed by the stress waves on the inner and outer faces of the diaphragm are dissimilar in length, the vibrations arriving at the periphery may be outof phase by a certain amount, and under these conditions adifferent type of vibration different frequency response will be ob tained from that which would be obtained from a single diaphragm. It is also to be noted that the inclusion of the air in the confined space between the diaphragms may act as a resonance chamber which will react upon the diaphragm to modify its characteristics.

will be obtained and a transmitted to the 1 In accordance with another form of my filed Mar. .11, 1927, thus producing a diiferent mode of vibrationof the diaphragm, and

a diiferent frequency response.

. In this arrangement, Im'ay provide a plurality of piezo-electric crystals contained within the diaphragm, each of which may be connected to the diaphragm at a different point, whereby vibrations may be initiated at symmetrical points other than the apex of the diaphragm in any desired phase relation.

Referring now more particularly to Figures 1, 2 and 3, 1 designates an inner diaphragm, 2 an outer diaphragm, and 3 the driving means which may, for example, be a piezo-electric crystal device, such as Rochelle salt exhibiting the Well known hour glass configuration; a stress plate 4 which may be of elastic metal such as steel is cemented or bolted, or both, to the top basal plane of the crystal 3, and driving rods 5 and 6 are suitably secured thereto at one end and at the other end to the apeXes of diaphragms l and 2. The bottom basal plane of the crystal 3 is mounted as by cementing-or bol ting upon a bottom stress plate 7 to which is secured a support 8 passing through a suitable openin in the diaphragm 2.

A pair of electrodes, 9 and 10, diagrammatically shown, are also provided, associated with crystal 3. These electrodes may be of any desired form, but preferably one will consist of an equatorial belt of conduct ing material such as metal foil or graphite paint extending around the outer surface of the crystal parallel to and intermediate the top and bottom basal planes. The other electrode may be one or both of the plates 4 and 7, or may alternatively be an internal electrode such as a bolt passing through the crystal.

Application of electrical oscillations to the electrodes 9 and 10 causes a torsional vibra tion of the crystal 3 as a result of which the top stress plate 4 tends to rotate about the crystal axis. This rotation "appears as substantially reciprocating mot-ion of the driving rods 5 and 6, which sets into vibration the apexe's of the diaphragms 1 and 2, thereby propagation of stress waves tocausin the ward 518 peripheries of these diaphragms,

which peripheries may be suitably secured together, as by cementing, or left free." In any event, by reason of the adjacent position or physical contact of the peripheral edges of diaphragms 1 and 2, as well as by reasons of the reaction of the air confined between these diaphragms, a relatively different mode of vibration is obtained from that which would be obtained where either of the diaphr'agms alone operated in unconfined air.

Referring now more particularly to Figures land "5, I have shown an arrangement in which the driving force is applied to points other than the apex of the diaphragm 2. In this instance, I provide a plurality of driving means suchas pie'zo-electric crystal devices, 1'6, 17, 18 and 19, each provided with a base stress plates 20, 21, 22 and 23 respectively, and top stress plates 24, 25, 26 and 27 respectively, suitably held in position upon the crystal by means of bolts 28, 29, 30 and 31 reelectrodes 35, 37, 39 and 41 formed by a loop at points 42 and 44 will at points 43 and 45. It will" 'a considerable number of spcctively passing through the crystals and the top and bottom stress plates. In addition, the stress plates may be cemented to the crystal if desired. The stress plates are all supported froma suitable central support 15 forming an extension of the base 8, and in this instance, passing into the interior space between the diaphragms through an opening at the apex of the diaphragm 2. This support 15 is preferably square in cross section and is extended to permit of the bolting'or cementing of the apex of the diaphragm 1 thereto. Each of the base plates 21, 22 and 23, is secured in position as shown in Figures 4 and 5, by means of suitable bolts and associated nuts 32 and 33, which anchor the crystals 16, 17, 18 and 19, in position as shown. The top stress plates 24, 25, 26 and 27, terminate in suitable driving means 42, 43, 44 and 45 respectively, secured to the diaphragm 2 in any suitable manner as by bolting or cementing. The diaphragm is preferably reenforced at the points of contact by suit able disks 50, 51, 52, 53 suitably secured thereto, which serve to apply the driving force over a relatively larger surface of the diaphragm than would be the case were they omitted. The crystal 16 is provided with electrodes 34 and 35, crystal 1? with electrodes 36 and 37, crystal 18 with electrodes 38 and 39, and crystal 1'9 with electrodes 40 and 41, of any suitable'type as heretofore described. The electrodes may be connected-in any desired manner so that each of the driving heads 42, 43, 44and 45 operates in phase, or out of phase with any other by connecting the electrodes similarly or dissimilarly: for example, if the internal bolts 28, 29, 30 and 31 constitute one electrode of crystals 16, 17, 18 and 19 each of these bolts maybe connected together sun to one source of the oscillations for driving the diaphragm. if the other of each crystal are of conducting material aboutthe crystal, each of these may be connected together and to the other terminal of the source, in which case the driving heads 42, 43, 44 and 45 will operate in phase, and the stress waves set up at points of connection of each of these driving heads to the diaphragm 2, will be the same. If, on the other hand, the connections to electrodes of crystals 16 and 18 be reversed, the stress waves initiated be out of phase with those initiated be seen that by connecting the various crystal electrodes as desired to obtain the desired phase relation of vibrations in various parts of the diaphragm and as modifiedby the re action of the diaphragm 1 and the air confined therebetiveen, a considerable number of modes of vibration may be obtained, and

variations in frequency response may be obtained.

While I have shown and described certain racing preferred forms of my invention, it will be apparent that modifications and changes may be made Without departing from they spirit and scope of my invention, as will be understood by those skilled in the art.

I claim:

1. A loud speaker comprising a pair of conical diaphragms of different altitudes having their peripheries secured together and their apexes disposed on the same side of the peripherial plane but spaced apart and driving mechanism disposed between the apexes and connected thereto for imparting vibrations to each of said. diaphragms.

2. A loud speaker comprising a pair of conical diaphragms of the same diameter but different altitude secured with their peripheries adjacent to each other and their apexes spaced apart on the same side of the peripherial planes and driving mechanism disposed between the apexes and connected thereto for imparting vibrations to each of said diaphragms.

3. A loud speaker comprising a pair of conical diaphragms having their peripheries of substantially the same diameter and secured together and having their apexes disposed on the same side of the peripherial plane and spaced apart and driving apparatus disposed within the space defined by the two cones and operatively connected to both of said diaphragms.

l. A loud speaker comprising a pair of conical diaphragms having a different solid angle at the apex, each of said diaphragms being mounted with their peripheries adjacent each other and driving mechanism disposed between the apexes and connected thereto for imparting vibrations to each of said diaphragms.

5. A loud speaker comprising a pair of conical diaphragms having a different solid angle at the apex and mounted with their peripheries adjacent each other, and having the apexes disposed on the same side of the peripherial plane and driving mechanism disposed between the apexes and connected thereto for imparting vibrations to each of said diaphragms. I

6. A loud speaker comprising a pair of conical diaphragms mounted with their peripheries adjacent and their concave sides the same direction and means for driving said diaphragm, said means being housed entirely within the area enclosed by said diaphragms.

7. A loud speaker comprising a pair of conical diaphragms mounted with their peripheries adjacent and their concave sides facing the same direction and means for driving said diaphragms, said means being included entirely in the space between said diaphragms and links extending from said means in opposite directions and connected to the apexes of said diaphragms for simultaneously driving said diaphragms.

8. A loud speaker comprising a plurality of cone diaphragms of substantially thesame diameter but of different altitude mounted I with the peripheries adjacent and with the apexes disposed upon the same side of the peripherial plane and means for driving said diaphragms, said means being contained entirely in the space between said diaphragms and means for applying the driving force developed by said driving means to said diaphragms at a plurality of points.

9. A loud speaker comprising two spaced conical diaphragms having different slopes, one of said diaphragms being disposed at least partly within the other and a driving mechanism disposed in the space between said diaphragms and operatively connected to both of said diaphragms.

Signed at New York in the county of New York and State of New York this 16th day of March A. D. 1927.

ALEXANDER McLEAN NICOLSON 

